The bimolecular lipid leaflet (lipid bilayer) postulated as the basic structural matrix of biological membranes is widely accepted. Recent experiments have made direct studies of lipid bilayers possible. As has been demonstrated by a number of investigators and ourselves, these artificially constituted bilayer lipid membranes of planar and spherical configuration (BLM and liposomes) possess many properties resembling those of biological membranes. At the present time, a bilayer lipid membrane upon suitable modification serves as a unique model for the biological membrane. The proposed project will be concerned with the biophysics of BLM and liposomes. The proposed research will be centered on the following: (1) continuing the current research program on the studies of the basic physical and electrochemistry of BLM, which should provide a more rational basis for further development; and (2) reconstituting specific biomembrane systems with lipid bilayers of either planar or vesicular configuration and their modifications so that simple physical, chemical and physiological processes may be isolated and analyzed in terms of the physical and chemical properties of the constituent compounds. An important objective of this work is to obtain quantitative data on lipid bilayers which it is hoped will provide a molecular basis for an understanding of the much more complex questions of transport, ion selectivity, energy transduction, redox reactions, and immunological properties in biological membranes.